Element with very high mechanical resistance and high vibration absorption and method for implementing the same

ABSTRACT

Element ( 1 ) with very high mechanical resistance and high vibration absorption, comprising at least one internal core ( 20 ) composed of at least one first material ( 2 ) having predominantly high mechanical characteristics, and united, through chemical bonding only, with at least one second material having predominantly highly elastic characteristics; the embodiment method consists in automatically uniting through chemical bonding a first material with predominantly high mechanical characteristics with at least a second material ( 3 ) with predominantly highly elastic characteristics in order to form a core ( 20 ) to be coated with at least a third material ( 11 ).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage of PCT/EP02/14469 filed 18 Dec.2002 and is based upon Italian national application Mi2002A000010 filed8 Jan. 2002 under the International Convention.

FIELD OF THE INVENTION

The present invention relates to an element with high mechanicalstrength and high vibration absorption, and to a method of making thesame.

BACKGROUND OF THE INVENTION

The element according to the present invention may be used preferablyfor handles on tools such as hammers, sledge hammers, tools used forbuffeting trees for fruit-picking, axes, and the like. It can also beused for manufacturing any structures that require high mechanical andworkability characteristics and high vibration absorptioncharacteristics at the same time, combined with special physicalproperties such as resistance against corrosion, absence of hygroscopyand porosity, shrinking and dilatation.

It is a well known fact that elements that must be held in the hand foruse, such as handles and the like, that possess mechanical strength andare able to absorb vibration, are traditionally manufactured in wood toguarantee good technological performance because of wood's fibrousnature (splitting and cutting capacity, flexibility, cleanliness andplasticity levels) combined with physiological properties (porosity,density, hygroscopy, homogeneity, shrinking and dilatation) and goodvibration absorption.

However, in certain cases the mechanical properties of wood (traction,compression, bending, cutting capacity, torsion) can be insufficient forcertain applications, for example when the predominant stress involvesstrong impact (impact stress) or flexion.

In these cases, results have shown that the wooden element used as ahandle in a wide variety of work sectors can break because of itsmorphology.

Moreover, with wear, wood can splinter, harming the user, and whensubject to atmospheric agents (for example, when left outside) becauseit is hygroscopic it tends to shrink or dilate thus provoking playbetween the wooden element and the other elements attached to it thatare generally made of metal.

To overcome these problems, other types of handle have been manufacturedwith a fiberglass-reinforced plastic core that acts as a coating and toprovide a correct grip.

However, these solutions have also created many problems, mainly due tothe fact that the fiberglass core transmits the vibrations provoked bytool use, and the vibrations are transmitted to the user's arm, almostwithout any cushioning, provoking consequential damage to the arm.

Moreover, when fiberglass is used for handles and the like, specialadhesives must be used to create correct bonding between the variouscomponents and this leads to a considerable extension of productiontime, the need for more labor, and an increase in production costs, aswell as the fact that all adhesives have varying aging times whichinfluence the chemical and physical characteristics.

The use of adhesives can be eliminated, but this means a longpreparation time for the mold in which the various components arearranged.

This situation has a considerable influence on production costs, andproduces unacceptable quantity levels.

OBJECT OF THE INVENTION

It is an object of the invention to provide an element with very highmechanical strength, and high vibration absorption, and a method ofmaking the same, which eliminate the technical problems encountered inprior art.

Another object is to provide an element that, as well as havingexcellent chemical and physical characteristics, is also able to cushionthe vibrations that are generated during use, very efficiently.

A further object of the invention is to provide an element and a methodfor producing said element without the need for specialize labor, andthat can be manufactured in a short time and using automated productionmethods.

A further object of the invention is to provide an element that isextremely reliable because of its long-lasting physical and chemicalcharacteristics that can be designed so that it is not subject todegeneration because of the inevitable deterioration of some of itscomponents, such as the adhesive.

A last, but by no means least, object of the invention is to provide anelement and a production method that are basically economical, and thatcan be performed using a pultrusion method that is basically automatic.

SUMMARY OF THE INVENTION

These and other objects, according to the present invention are attainedby providing an element with high mechanical strength and high vibrationabsorption which comprises at least one internal core composed of atleast one first material with predominantly very high mechanicalstrength, combined through chemical bonding only with at least onesecond material with predominantly very high elastic characteristics.

The present invention also is a method of producing an element with veryhigh mechanical strength and high vibration absorption levels, whichconsists of automatically uniting through chemical bonding, a firstmaterial with predominantly very high mechanical strength, with at leastone second material with predominantly very highly elasticcharacteristics in order to form a core that can be coated with at leastone third material. The first and second materials can be bonded withoutthe use of adhesives. The first material can be composed of athermoplastic resin in which a plurality of natural and/or syntheticfibers are embedded. The synthetic fibers can be composed of glassfiber.

The second material can be composed of an elastomeric polymer. Thethermoplastic resin-can be an engineered polyurethane thermoplasticpolymer, industrially recognized under the name ETPU (engineeringthermoplastic polyurethane). The second material can alternatively bethermoplastic polyurethane.

The core can covered with a layer in a third material composed of anelastomeric polymer. This core can comprise at least two elongatedelements created using pultrusion. The elongated elements can berod-shaped or disk-shaped.

According to a feature of the invention, a bearing made of the secondmaterial is inserted between the elongated elements. The rod-shapedelements can have at least one flat surface and one curved surface, thebearing being inserted between the flat surfaces of the adjacentrod-shaped elements.

The method of the invention for implementing an element with highmechanical strength and high vibration absorption, comprises theautomatic union through chemical bonding of a first material havingpredominantly high mechanical characteristics, with at least a secondmaterial having predominantly highly elastic characteristics, in orderto form a core which is coated with at least one third material. Theunion between the first and second material occurs without the use of anadhesive, but with the application of heat at an establishedtemperature.

The material can be composed of a thermoplastic resin in which aplurality of natural and/or synthetic fibers are embedded. The syntheticfibers are composed of glass fiber and the second material can becomposed of thermoplastic polyurethane, especially engineeredpolyurethane thermoplastic polymer, industrially recognized under thename ETPU (engineering thermoplastic polyurethane) or an elastomericpolymer, preferably is of polyurethane type.

The method can include at least one stage in which the first material isobtained through pultrusion. The method preferably includes at least onecoextrusion stage at an established temperature to unite the firstmaterial with the second material and includes a thermoforming stage tomodel the third material into an ergonomical shape.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing:

FIG. 1 shows a cross section of an element defined as a handle accordingto the finding, and, shown in dotted lines, a tool which in this casepurely as an example, is shown as the head of a hammer; and

FIGS. 2 and 3 show respectively in cross section and in perspective, adifferent embodiment of the element from that in FIG. 1.

SPECIFIC DESCRIPTION

With reference to the above-mentioned Figures, the illustrated elementwith high mechanical strength and high vibration absorption isidentified in all Figures with the reference numeral 1.

Element 1, which, as has been stated above, can preferably be an elementused as a handle for certain tools, or used for buffeting plants or thelike, comprises at least one internal core 20, composed of at least onefirst material 2 with predominantly very high mechanical strengthcombined through chemical bonding only and without the use of adhesiveswith at least one second material 3, with predominantly very highlyelastic characteristics.

In particular, the structure of a tool handle will be describedhereinbelow as a preferred but nonlimiting embodiment, taking intoaccount, as has been previously stated, that any element that requiresthe above-mentioned chemical and physical characteristics can also beproduced for other uses.

In the case of a tool handle for example, the first material 2 is usedto form two or more rod-shaped elements 4 that are substantially thesame length as the handle to be manufactured.

The second material 3 is inserted between these rod-shaped elements aswill be further described below, to form a real cushion 5 to absorbvibrations that tend to be transmitted along the two rod-shaped elementswhen the handle is subjeced to impact involved during tool use.

Advantageously, the core 20, is obtained by simply combining the firstmaterial 2 with the second material 3 through chemical bonding obtainedwith the application of heat at an established temperature and withoutthe use of adhesives between the first and second material, or throughthe use of an adhesive in the case of adhesion incompatibility betweenthe two materials.

This simplifies and speeds up the creation of the core 20, and alsopermits the creation without the need for specialized labor for theproduction preparation, providing considerable advantages because of thelarge reduction in cost and time.

Suitably the first material (such as TPV, PP, PET) is made of athermoplastic resin in which a plurality of natural or synthetic fibersare embedded (e.g. glass fiber), and the second material is made of anelastomeric polymer such as thermoplastic polyurethane.

As an example, the first material can be an engineered polyurethanethermoplastic polymer, industrially recognized under the name ETPU(engineering thermoplastic polyurethane) and the second materialcomprises an elastomeric polymer, preferably polyurethane type.

Element 1 can also be coated over the core 20, with a covering layer 6,made of an elastomeric polymer.

Advantageously, the rod-shaped elements 4, are produced using apultrusion method.

A coextrusion head is used to combine in a linear and continuous mannerthe two rod-shaped elements 4, produced with pultrusion, with the secondmaterial 3, to form the cushioning element 5.

For example, the coating layer 6, made of the third material composed ofan elastomeric polymer can be applied onto the core 20 by a secondcoextrusion head.

In the case of handles shaped differently from the cylindrical form, forexample ergonomically shaped handles, the third material in elastomericplastic 6, can undergo a thermoforming stage.

In a constructive variant, the chemical bonding between the first andsecond material can be performed directly during the impregnation stageof the glass fiber with the thermoplastic resin.

In the case illustrated in FIG. 1, each of the rod-shaped elements 4,has a flat surface 10, and a curved surface 11.

This means that the cushion 5, made from the second material, can beinserted between the two flat surfaces 10.

With this solution, during strong impact the main flexion in the handlewill occur along the two flat surfaces 10 that will form a slidingmovement between both elements due to the elasticity of the cushioninserted between the two flat surfaces.

At the same time, the vibrations will be cushioned and will not be ableto spread along the handle.

In the case illustrated in FIG. 2, the rod-shaped elements are four innumber, and a cross-shaped bearing made from the second material isinserted therebetween.

In this case flexion can occur around all 360° and vibration cushioningwill be excellent.

Naturally the configuration of the rod-shaped elements can be of anytype according to necessity.

For example, in certain cases the rod-shaped elements could be disks orthe like.

The operation of the element with high mechanical resistance and highvibration absorption described in this invention is evident from thedescriptions and illustrations.

For example, FIG. 1 shows the head of a hammer in dotted lines and isidentified by the reference numeral 15.

When a hammer is used to hit with strong impact, the rod-shaped elementstend to transmit vibrations that are absorbed by the bearing 5, andcoating 11.

Moreover, the slight sliding motion is created between the tworod-shaped elements in order to absorb impact further.

The present invention also refers to a method for the realization of anelement with high mechanical resistance and high vibration absorption.

The method consists in the automated union without the use of adhesives,of a first material with predominantly high mechanical characteristicswith at least one second material with predominantly highly elasticcharacteristics.

In particular, advantageously, this union is created through chemicalbonding that is performed with the application of heat at an establishedtemperature.

In a constructive variant, in the case where the first and secondmaterials are reciprocally incompatible for bonding adhesion, they canbe glued together with a chemical bonding adhesive.

In this way a core is formed, that may be eventually coated with atleast one third material.

Advantageously, the first material is created using a thermoplasticresin in which a plurality of natural or synthetic fibers are embedded(for example, glass fiber), and the second material is created using anelastomeric polymer, such as thermoplastic polyurethane.

As an example, the first material can be an engineered polyurethanethermoplastic polymer, industrially recognized under the name ETPU(engineering thermoplastic polyurethane) and the second materialcomprises an elastomeric polymer, preferably polyurethane type.

It has been established that the element with high mechanical strengthand high vibration absorption, and the method for implementing the sameaccording to the invention are particularly advantageous because theelement is able to absorb vibration very efficiently and the productionmethod is rapid and does not require specialized labor, thus being verycost-effective.

The element with high mechanical resistance and high vibrationabsorption, and the method for implementing the same according to theinvention can be produced with numerous variants and modifications, allof which are included within the scope of the invention; moreover, allcomponents can be replaced by elements that are technically equivalent.

1-24. (canceled)
 25. An element having high mechanical strength and highvibration absorption comprising: an internal core composed of at leastone core member constituted of at least one first material consisting ofa thermoplastic resin in which a plurality of natural and/or syntheticfibers are embedded and having predominantly high mechanicalcharacteristics, and at least one second material with predominantlyhighly elastic characteristics bonded to the first material without theuse of adhesives; and a layer covering said core.
 26. The elementdefined in claim 25 wherein said fibers are composed at least in part ofglass fiber.
 27. The element defined in claim 26 wherein said secondmaterial is an elastomeric polymer.
 28. The element defined in claim 27wherein said thermoplastic resin is engineered polyurethanethermoplastic polymer (ETPU).
 29. The element defined in claim 27wherein said second material is composed of thermoplastic polyurethane.30. The element defined in claim 29 wherein said layer is an elastomericpolymer.
 31. The element defined in claim 30 wherein said core iscomprised of at least two discrete elongated members of said firstmaterial produced by pultrusion and extending along the entire length ofsaid elements, a bearing of said second material being inserted betweensaid elongated elements.
 32. The element defined in claim 31 whereinsaid members are rod-shaped or disk-shaped.
 33. The element defined inclaim 32 wherein said members are rod-shaped and each have at least oneflat surface and one curved surface, said bearing being inserted betweenand bonded to flat surfaces of said members.
 34. The element defined inclaim 33 in the form of a handle for a hand tool.
 35. A method of makingan element with high mechanical strength and high vibration absorption,comprising the steps of: (a) forming at least two discrete elongatedmembers of a length capable of extending along an entire length of saidelement and composed of a first material having predominantly highmechanical characteristics; (b) inserting between said members andautomatically bonding thereto by chemical bonding a bearing of at leasta second material having predominantly highly elastic characteristicswhereby said members and said bearing form a core; and (c) coating saidcore with at least one third material.
 36. The method defined in claim35 wherein the bonding of the first material and the second material iseffected by the application of heat and without the use of an adhesive.37. The method defined in claim 36 in which said material is athermoplastic resin in which a plurality of natural and/or syntheticfibers are embedded.
 38. The method defined in claim 37 wherein saidfibers include glass fibers.
 39. The method defined in claim 38 whereinsaid second material is a thermoplastic polyurethane.
 40. The methoddefined in claim 39 wherein said thermoplastic resin is engineeredpolyurethane thermoplastic polymer (EPTU).
 41. The method defined inclaim 40 wherein said third material is composed of an elastomericpolymer.
 42. The method defined in claim 41 wherein said members areshaped at least in part by pultrusion.
 43. The method defined in claim42 wherein said core is shaped at least in part by coextrusion at atemperature sufficient to bond said first and second material together.44. The method defined in claim 43, further comprising the step ofthermoforming said third material to shape said element into anergonomic shape.